Getting Started with System Identification

System identification is a series of processes for building the mathematical models of a dynamic system by using the stimulus and response data of the dynamic system. A direct current (DC) servomotor is a typical example of dynamic systems. A DC servomotor generates rotation motion through the magnetic interaction between a current-carrying conductor and an external magnetic field.

A DC servomotor is a common actuator in a control system. To estimate the model of a DC servomotor, you need to create a model that contains unknown coefficients according to the application requirements. For example, if you plan to create a model that you can use with a proportional-integral-derivative controller for a DC servomotor, you can create the following transfer function model, G(s), for the measured rotational speed of the shaft, ω, and the driving voltage, U, of the DC servomotor.

Perform system identification on the previous transfer function model to estimate the coefficients, b₀, a₀, a₁, and a₂, of the transfer function, on the basis of the measured rotational speed, ω, and driving voltage, U.

The following figure shows the processes of identifying the model of a DC servomotor.

Read through the following topics to perform system identification on a DC servomotor by using the System Identification VIs.

• Choosing a proper dynamic system model by using physical modeling
• Exciting the system and acquiring data
• Identifying dynamic system models
• Validating and analyzing dynamic system models
• Converting dynamic system models to control design models